DYNAMIC former Noosa player Moses Mbye is poised to become the Canterbury Bulldogs' X-factor against the heavily favoured Rabbitohs in tonight's grand final, former premiership-winning coach Michael Hagan believes.

The Queensland assistant coach said Des Hasler would likely introduce Mbye at dummy-half before half-time and let the wily 21-year-old wreak havoc on South Sydney's worn-out forward pack.

"I'm sure Des would have something up his sleeve and maybe just before half-time when the game has opened up a touch is when he comes into the game," Hagan said.

"He could make a real impact when he comes on."

Hagan, who played in two premiership-winning Canterbury teams in the 1980s and coached Newcastle to the 2001 title, said Hasler was unlikely to put Mbye in the starting line-up as a replacement for injured captain Michael Ennis, who was officially ruled out yesterday.

On Tuesday, Hasler named Ennis in the No.9 with Mbye on an extended bench, but was coy when asked about his plan if Ennis could not play and did not clarify his intentions yesterday. "He would probably come into the game a little later and maybe Reni (back-rower Reni Maitua) would start," Hagan said.

"I JUST think maybe they need some bigger defenders in the middle straight up, but I doubt Reni would get through 80 minutes in the middle."

If Mbye plays tonight it will be the second time in two years a Noosa player has graced the NRL's biggest stage, with Jake Friend helping the Roosters win last year's premiership.

Several former and current players, including three-time Dally M winner Johnathan Thurston, are expecting Mbye to play.

Hagan said the ballplaying ability Mbye had shown in his eight NRL games and a simple game-plan would make up for his inexperience as a dummy-half.

"They wouldn't want to complicate the game - I'm sure Des Hasler wouldn't have a complicated game-plan for tomorrow anyway - so you just really need to be tidy and do your job well," Hagan said.

"Trent and Josh (halfback Trent Hankinson and five-eighth Josh Reynolds) will be the main guys, so he's just got to make sure he's doing his job.

"You're not looking for too many trick shots from him."

Hagan said it was just the start of things to come for Mbye.

"He might come into that emerging (State of Origin) squad calculation in January ... James Segeyaro and Jake Friend have been in those emerging squads for a number of years and so have a few other guys, but you've always got to have a couple of other contingencies up your sleeve and he might be one of them," he said.